1. Field of the Invention
This invention relates to an apparatus, a method, and a computer program product for supporting communication through translation between a plurality of languages.
2. Description of the Related Art
In recent years, with the development of the natural language processing technique, a machine translation system in which a text written Japanese, for example, is translated into another language such as English has come to find practical applications and the use thereof has widely extended.
The development of the speech processing technique, on the other hand, has led to the use of a speech dictation system capable of aurally inputting a character string of the natural language by converting the utterances uttered by the user into characters and a speech synthesis system in which the sentences obtained as electronic data or a character string of the natural language output from the system are converted to a speech output.
Also, the progress of the image processing technique has realized a character recognition system in which the sentences in the image can be converted into a machine readable character data by analyzing the character image picked up by a camera or the like. Further, the advance of the handwritten character recognition technique has made possible a technique in which a handwritten text input by the user through a pen input unit or the like is converted into a machine readable character data.
The globalization of the culture and the economy, on the other hand, has increased the chance of communication between persons having different mother tongue. In view of this, demand has heightened for a communication support apparatus in which the natural language processing technique, the speech processing technique, the image processing technique and the handwritten character recognition technique described above are coordinated to support the communication between persons of different mother tongue.
The communication support apparatus described below, for example, is conceivable. First, a Japanese input by voice or pen from a Japanese-native speaker is converted to a machine readable Japanese text using the speech recognition technique or the handwritten character recognition technique. Next, the text is translated into an English text of an equivalent meaning using the machine translation technique, and the result is presented as an English character string, or presented to an English-native speaker in the form of the speech in English using the speech synthesis technique. On the other hand, an English input uttered or input by pen from an English-native speaker is presented in the form of a translated Japanese text to a Japanese-native speaker by executing the reverse process. Using this method, efforts are under way to implement a communication support apparatus capable of bilateral communication between persons having different mother tongue.
As another example, a communication support apparatus described below may be conceived. First, the image of a character string written on a local sign board or a warning expressed in English is picked up by a camera. Next, the character string the image of which has been picked up is converted into a machine readable English character string data using the image processing technique and the character recognition technique. Further, the English language text is translated into a Japanese text of an equivalent meaning using the machine translation technique, and the resulting Japanese character string is presented to the user. As an alternative, the text is presented to the user as a speech in Japanese using the speech synthesis technique. The development is under way to realize a communication support apparatus using this method by which a person who can speak and understand only Japanese and traveling in an English speaking area can understand an English text on a sign board or a warning.
With this communication support apparatus, it is very difficult to acquire a correct, error-free candidate through the process in which the text input in the source language by the user is recognized by the speech recognition process, the handwritten character recognition process or the image character recognition process and converted into a machine readable text data. Generally, therefore, the processing of a plurality of candidates for interpretation results in ambiguity.
Also in the machine translation process, ambiguity is caused when converting the source language sentence to a semantically equivalent the target language sentence, and in the presence of a plurality of translation sentence candidates, a semantically equivalent translation sentence cannot be uniquely selected, thereby often making it impossible to obviate the ambiguity.
The cause of ambiguity is probably derived from the fact that the source language sentence is an ambiguous expression having a plurality of interpretations, the highly context-dependent expression of the source language sentence develops a plurality of interpretations, or the different linguistic and cultural backgrounds and the different concept system between the source language and the target language results in a plurality of translation candidates.
In order to obviate this ambiguity, if there are a plurality of candidates, a method has been proposed in which the candidate first obtained is selected or a method in which a plurality of candidates are presented to the user allowing him to select one of them. A method has also been proposed in which a plurality of candidates, if any, are scored according to some criterion and a candidate high in score is selected. Japanese Patent Application Laid-open No. H07-334506 (hereinafter referred to as First Document), for example, proposes a technique in which a translation word having a high similarity of the concept remembered from the word is selected from a plurality of words obtained as the result of translation thereby to improve the quality of the translated text.
The method of First Document poses the problem, however, that although the burden on the user to select a translation word is eliminated, the criterion for scoring is difficult to set, and therefore the optimum candidate is not always selected and a translation sentence departing from the intention of the source language sentence may be output.
Further, the communication support apparatus described above is intended to support the communication between users having different languages which they can understand. Generally, the user cannot understand the target language output, and therefore the method allowing the user to select one of a plurality of candidates poses the problem that a translation error, if any, cannot be discovered and corrected.
When the communicative intention of a speech cannot be transmitted successfully to the other party due to a translation error, therefore, the user generally inputs the same text again. In the process, assume that a communication support apparatus is implemented by combining the speech recognition and the language translation. Even in the case where a translation error is caused by the failure of speech recognition, the speech recognition may succeed and the translation error may be avoided when the speech recognition process is executed again.
As long as a translation error occurs in the translation process after a successful speech recognition, however, the speech recognition output result still remains unchanged by the user inputting again the same text, and therefore the same translation error is repeated in the process and the same translation error cannot be avoided. Also, the repeated input operation increases the burden on the part of the user.